In a large bowl, mix together all the dry ingredients.
Mix the liquid ingredients together well and pour gradually into the bowl with the dry ingredients.
Using a spatula or your hands, mix and knead the mixture until you have a stretchy, elastic dough. Turn out onto a work surface or board and knead for a further few minutes to develop the gluten.
Bring a large pan of water to a boil. Tear off walnut sized pieces of the seitan dough and carefully drop them into the simmering pan. Continue this process until you have used all of the dough. Turn the heat down to low and simmer for 40 minutes.
Preheat oven to 180°C (Gas Mark 4, 350°F) and lightly oil a baking dish large enough to hold all the seitan bites. Drain the seitan and set aside to steam dry in a colander.
In a saucepan, mix together all of the ingredients for the sauce and heat gently, stirring occasionally.
Arrange the seitan pieces in the baking tray and pour over 4 tbsp of the sauce. Toss to coat all the bites in the sauce and transfer to the oven to cook for 20-30 minutes. They should be golden, sticky and slightly chewy in texture.
Serve hot or cold, on a platter with the extra sauce on the side for dipping.
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